The normal lung has an alveolar "basement membrane" which supports and functionally-links the alveolar epithelium and capillary endothelium. This structure consists of extensively apposed epithelial and endothelial basal laminas and relatively small amounts of associated reticular matrix. It has been hypothesized that the epithelial basal lamina contributes to the maintenance of a functional alveolar architecture, provides a substratum for the proliferation and differentiation of type II pneumocytes, and mediates interactions between these cells and components of the underlying extracellular matrix. It has also been suggested that structural integrity of the basal lamina is important for restoration of a functioning parenchyma following injury and that alterations in basal lamina structure could contribute to the evolution of certain acute and chronic lung diseases. Although collagens are considered to be important structural and functional components of basement membranes in many tissues, relatively little is known about the contribution of these proteins to the structure and function of the alveolar "basement membrane". The present proposal has 3 main aims: (1) to utilize lung organ cultures to study the biosynthesis, extracellular deposition, and turnover of pulmonary "basement membrane" procollagens, (2) to utilize primary cultures of type II pneumocytes to further define the contribution of these cells to the synthesis of "basement membrane" procollagens and to the metabolism of the alveolar epithelial basal lamina, and (3) to examine the possible role of extracellular matrix in modulating the biosynthesis and metabolism of procollagen(s) and other matrix macromolecules synthesized by pulmonary epithelial cells in vitro. These studies will provide the basis for examining the mechanisms of lung damage involved in lung diseases, such as preliminary fibrosis, where there is extensive remodeling of the lung's architecture.